A.1.2.14-2.15 Hershey-Chase and Chargraffe

Front

What role did scientists believe chromosomes played in the late 1800s?

Back

Scientists were convinced that chromosomes played a role in heredity and that the hereditary material had a chemical nature.

Front

What were chromosomes known to be composed of?

Back

Chromosomes were known to be composed of protein and DNA.

Front

Why did most biologists consider protein as the likely genetic material until the 1940s?

Back

Protein was considered the likely genetic material because it contains 20 different amino acid subunits, whereas DNA has just four types of nucleotide. Proteins also had many identified specific functions, and variety and specificity were considered essential for hereditary material.

Front

What organism did Hershey and Chase use to identify the genetic material?

Back

Hershey and Chase used the T2 bacteriophage to identify the genetic material.

Front

What is the composition of the T2 bacteriophage?

Back

The T2 bacteriophage has a coat composed entirely of protein, with DNA inside the coat.

Front

What was known about viruses in the 1950s regarding host cells?

Back

It was known that a virus can transform a host cell to produce viral proteins, indicating that viral genes must have been injected into the host cell.

Front

How did Hershey and Chase differentiate between DNA and protein in their experiment?

Back

They used radioactive isotopes: proteins with radioactive (35S) sulfur and DNA with radioactive (32P) phosphorus.

Front

What method did Hershey and Chase use to separate the non-genetic component of the virus?

Back

They used a blender to separate the non-genetic component of the virus.

Front

What was the purpose of centrifuging the culture solution in Hershey and Chase's experiment?

Back

Centrifuging was used to concentrate the cells in a pellet, which were expected to contain the radioactive genetic component of the virus.

Front

What hypothesis did scientists have about the structure of DNA before it was known?

Back

Scientists hypothesized that DNA would contain a repeating sequence of the four bases, known as the tetranucleotide hypothesis.